Robust Capsule Research Articles

Fast Robust Capsule Network With Dynamic Pruning and Multiscale Mutual Information Maximization for Compound-Fault Diagnosis

Rotating machinery, such as ventilators and water pumps, are crucial components in modern industry, of which safety monitoring requires intelligent fault diagnosis. Feature representation learning is essential in the intelligent fault diagnosis of rotating machinery. In this study, a fast robust capsule network augmented with a dynamic pruning technique and a mutual information loss is proposed. The capsule layer overcomes limitations in pooling layers and scale-invariant feature transformation by learning tensor representations of features. The dynamic pruning method employs a dropout-like strategy to prevent repeated calculations and reduce the scale of parameters to simplify the network topology while increasing robustness. The enhanced agreement function limits the similarity of capsules in the same layer to avoid homogeneous features. The local and global discriminators are designed to learn and obtain mutual information in two aspects. The resulting multiscale mutual information loss for the proposed model successfully increases the model's representation learning capacity by integrating local and global information. The performance of the proposed method is successfully verified on several datasets with various noise levels obtained from a simulation platform.

Analytical physical models for cryogenic double-shell capsule design driven by Z-pinch dynamic Hohlraum

The Z-pinch dynamic Hohlraum (ZPDH) is a promising indirect-drive approach for inertial confinement fusion. The volume ignition capsule is more robust than the hot-spot ignition capsule for ZPDH due to the fact that the ZPDH radiation drive source has a high energy but low symmetry. Focusing on the ignition design of cryogenic double-shell volume ignition capsules using ZPDH radiation sources, three analytical physical models, including the ablation and implosion model, the shell collision model, and the burn fraction model, are established to quantitatively characterize the relation of capsule parameters. Robust capsule designs are then determined based on these analytical models together with 1D radiation hydrodynamics simulations. The results show that under the 10 ns, 308 eV radiation drive source produced by ZPDH with 50 MA load current, capsules with a large range of parameters can ignite. The fusion yield of the recommended capsule is 16.0 MJ, and the absorbed energy is 1.28 MJ.

Scene Recognition Using Deep Softpool Capsule Network Based on Residual Diverse Branch Block.

With the improvement of the quality and resolution of remote sensing (RS) images, scene recognition tasks have played an important role in the RS community. However, due to the special bird’s eye view image acquisition mode of imaging sensors, it is still challenging to construct a discriminate representation of diverse and complex scenes to improve RS image recognition performance. Capsule networks that can learn the spatial relationship between the features in an image has a good image classification performance. However, the original capsule network is not suitable for images with a complex background. To address the above issues, this paper proposes a novel end-to-end capsule network termed DS-CapsNet, in which a new multi-scale feature enhancement module and a new Caps-SoftPool method are advanced by aggregating the advantageous attributes of the residual convolution architecture, Diverse Branch Block (DBB), Squeeze and Excitation (SE) block, and the Caps-SoftPool method. By using the residual DBB, multiscale features can be extracted and fused to recover a semantic strong feature representation. By adopting SE, the informative features are emphasized, and the less salient features are weakened. The new Caps-SoftPool method can reduce the number of parameters that are needed in order to prevent an over-fitting problem. The novel DS-CapsNet achieves a competitive and promising performance for RS image recognition by using high-quality and robust capsule representation. The extensive experiments on two challenging datasets, AID and NWPU-RESISC45, demonstrate the robustness and superiority of the proposed DS-CapsNet in scene recognition tasks.

Optimized synthesis of isocyanate microcapsules for self-healing application in epoxy composites

Microcapsules containing isophorone diisocyanate were fabricated in oil-in-water emulsion. The emulsification effect of different emulsifiers during the capsule synthesis was systematically investigated by optical microscope. Three kinds of shell materials were discussed to obtain the high core content, smooth-surfaced, and robust capsule by scanning electronic microscope and Fourier transform infrared spectroscopy. Self-healing performance of corresponding self-healing epoxy composites was fully evaluated by accelerated corrosion test and mechanical test. The results demonstrated that high core content and smooth-surfaced capsules with dense composite shell could be synthesized in polyvinyl alcohol emulsion, and the core content of the optimized capsules was determined as 71.3–84.6 wt% at the capsule size from 35 µm to 154 µm. In addition, the optimized capsules had good processing properties and the corresponding self-healing epoxy composites exhibited excellent core release and self-healing performance.

Graphene oxide–silica hybrid capsules for sustained fragrance release

Encapsulation of active or valuable cargoes has become one of the most important methods for controlled delivery and release. However, many existing capsule technologies suffer from scalability issues, and capsules from surfactant- or polymer-stabilised emulsions tend to have weak shells or limited stability. Here we present a robust and scalable method for the surfactant-free preparation of silica hybrid capsules templated from Pickering emulsions stabilised by graphene oxide. These capsules are produced using a single step, undemanding formulation process with cheap and scalable precursors. The mechanical and chemical stability provided by the silica shell grown around these droplets is explored using surface pressure measurements and atomic force microscopy, demonstrating that a rigid and robust capsule is produced from higher loadings of silica precursor. In order to demonstrate the utility of these capsules, the sustained release of a fragrance molecule (vanillin) from the capsules is monitored, and compared to release from unencapsulated vanilla oil. It is seen that the capsules retain the fragrance for multiple weeks, offering new pathways for scalable encapsulation systems for the delivery of valuable actives.

Pharmaceutical 3D printing: Design and qualification of a single step print and fill capsule

Fused deposition modeling (FDM) 3D printing (3DP) has a potential to change how we envision manufacturing in the pharmaceutical industry. A more common utilization for FDM 3DP is to build upon existing hot melt extrusion (HME) technology where the drug is dispersed in the polymer matrix. However, reliable manufacturing of drug-containing filaments remains a challenge along with the limitation of active ingredients which can sustain the processing risks involved in the HME process. To circumvent this obstacle, a single step FDM 3DP process was developed to manufacture thin-walled drug-free capsules which can be filled with dry or liquid drug product formulations. Drug release from these systems is governed by the combined dissolution of the FDM capsule ‘shell’ and the dosage form encapsulated in these shells. To prepare the shells, the 3D printer files (extension ‘.gcode’) were modified by creating discrete zones, so-called ‘zoning process’, with individual print parameters. Capsules printed without the zoning process resulted in macroscopic print defects and holes. X-ray computed tomography, finite element analysis and mechanical testing were used to guide the zoning process and printing parameters in order to manufacture consistent and robust capsule shell geometries. Additionally, dose consistencies of drug containing liquid formulations were investigated in this work.

Magnetic implants in the tongue for assistive technologies: Tests of migration; oromotor function; and tissue response in miniature pigs

ObjectiveUncertain biological consequences of titanium-magnet (Ti-mag) tongue implants constrain application of the Tongue Drive System (TDS), a brain-tongue-computer interface for individuals with severe physical impairment. Here we describe oromotor function and tongue tissue response following Ti-Mag implantation and explantation in the miniature pig, an animal model with a tongue similar in size to humans. DesignA 1.8×6.2mm Ti-mag tracer was implanted into the anterior tongue in five Yucatan minipigs. X-rays were taken immediately and >six days after implantation to evaluate tracer migration. In three minipigs, the tracer was explanted >16days after implantation. Twenty-five days post-explantation, tongue tissue was harvested and processed for histological and immunohistochemical (IHC) markers of healing. In two minipigs tissue markers of healing were evaluated post-mortem following >12days implantation. Drink cycle rate (DCR) was characterized to determine the impact of procedures on oromotor function. ResultsNeither implantation (N=5) nor explantation (N=3) changed DCR. X-rays revealed minimal tracer migration (N=4, 0–4mm). By histology and IHC a robust capsule was present two weeks post-implantation with limited fibrosis. Explantation produced localized fibrosis and limited muscle remodeling. ConclusionsThese findings suggest the safety of Ti-mag anterior tongue implants for assistive technologies in humans.

Bioinspired Layer-by-Layer Microcapsules Based on Cellulose Nanofibers with Switchable Permeability.

Green, all-polysaccharide based microcapsules with mechanically robust capsule walls and fast, stimuli-triggered, and switchable permeability behavior show great promise in applications based on selective and timed permeability. Taking a cue from nature, the build-up and composition of plant primary cell walls inspired the capsule wall assembly, because the primary cell walls in plants exhibit high mechanical properties despite being in a highly hydrated state, primarily owing to cellulose microfibrils. The microcapsules (16 ± 4 μm in diameter) were fabricated using the layer-by-layer technique on sacrificial CaCO3 templates, using plant polysaccharides (pectin, cellulose nanofibers, and xyloglucan) only. In water, the capsule wall was permeable to labeled dextrans with a hydrodynamic diameter of ∼6.6 nm. Upon exposure to NaCl, the porosity of the capsule wall quickly changed allowing larger molecules (∼12 nm) to permeate. However, the porosity could be restored to its original state by removal of NaCl, by which permeants became trapped inside the capsule's core. The high integrity of cell wall was due to the CNF and the ON/OFF alteration of the permeability properties, and subsequent loading/unloading of molecules, could be repeated several times with the same capsule demonstrating a robust microcontainer with controllable permeability properties.

Fabrication of compact poly(methyl methacrylate-co-butyl methacrylate-co-acrylic acid) microcapsules for electrophoretic displays by using emulsion droplets as templates

Microcapsules with smooth, transparent, and compact walls used for electrophoretic displays (EPDs) were prepared and characterized. The approach to fabricate EPD microcapsules was based on templating an oil-in-water emulsion stabilized by monodispersed poly(methyl methacrylate-co-butyl methacrylate-co-acrylic acid) latex particles synthesized by dispersion polymerization. The individual latex particles were then transformed into robust capsule walls by successively using solvent swelling, covalent cross-linking, and sintering. The diameter of the emulsion droplets was controlled by changing the concentration of latex in the emulsion, and the thickness of the wall changed according to the diameter of the latex particles. These microcapsules for EPDs were applied successfully in preparing a clock display panel controlled by a single-chip microprocessor operated at a low direct current voltage, demonstrating that these microcapsules can be used in EPDs.

Hydrogen-Bonded Capsules in Water

Hydrogen-bonded capsules constrain molecules into small spaces, where they exhibit behavior that is inaccessible in bulk solution. Water competes with the formation of hydrogen bonds, and other forces for assembly, such as metal/ligand interactions or hydrophobic effects, have been applied. Here we report the reversible assembly of a water-soluble cavitand to a robust capsule host in the presence of suitable hydrophobic guests. The complexes are characterized by conventional NMR methods. Selectivity for guest length and fluorescence quenching of a stilbene guest are used as evidence for hydrogen bonding in the capsule.

Flow following sensor particles—Validation and macro-mixing analysis in a stirred fermentation vessel with a highly viscous substrate

A group of flow following sensor particles was validated under real flow conditions in a highly viscous substrate in a 1000L model fermenter vessel, equipped with a pitched blade impeller, which was operated at two different axial positions in an intermittent mixing regime. The neutrally buoyant sensor particles track basic hydrodynamic and process parameters, namely hydrostatic pressure (giving the axial position), temperature and acceleration. The sensors are connected to a measurement electronics, which is enclosed in a robust capsule that can resist the harsh conditions in an industrial mixing process. The results show that the sensor particles still reflect the flow conditions in the vessel qualitatively. Moreover, the sensor particle data allow estimation of macro-mixing parameters, such as circulation time distributions and average circulation times.

PH-responsive colloidosomes and their use for controlling release

In the past eight years, several examples of colloidosome microcapsules have been developed. Such microcapsules systems are offering alternative options for the encapsulation and release of active ingredients on the basis of the size exclusion properties of their colloidal membranes. Here, we use latex particles sterically stabilised with a responsive polymer as the building blocks for the colloidosome microcapsule membranes and demonstrate that the designed microcapsules can be used as a pH-responsive system to control the release of water-soluble species on the basis of size exclusion. For their manufacture, an oil-in-water emulsion is prepared using the latex particles to stabilise the emulsion. The latex particles are reacted in situ, using an oil-soluble cross-linker, to permanently link the steric polymers on adjacent particles, thus producing a robust capsule shell. The oil core is subsequently removed from the encapsulated emulsion droplets using a solvent exchange mechanism to give water-containing microcapsules suspended in water. As the oil is removed, the microcapsules initially collapse on themselves but they can be easily re-swollen to their initial spherical shape using a combination of polymer expansion within the membrane and induced chemical potential differences between the microcapsule cores and the bulk. We show here that the responsive polymer on the surface of the constituent particles within the monolayer forming the microcapsule membrane can be induced to expand and contract through changes in the dispersion pH as a result of its weakly basic nature. Using a fluorescently-labelled dextran molecule, we demonstrate its successful uptake within the core of the microcapsules at low pH where the capsule membrane is expanded and the pore size is maximised. Altering the pH to higher values results in the contraction of the membrane and closing of the surface pores; under these conditions we show that the dextran can be successfully retained within the microcapsules. Finally, we demonstrate the pH-dependent release of the labelled sugar by readjusting the pH to acidic conditions.

Preparation and Redox-Controlled Reversible Response of Ferrocene-Modified Poly(allylamine hydrochloride) Microcapsules

Single-component microcapsules were fabricated by the in situ reaction of ferrocenecarboxaldehyde (Fc-CHO) with poly(allylamine hydrochloride) (PAH) doped inside CaCO(3) microparticles, followed by core removal. The PAH-Fc microcapsules had very thick shells with remnant PAH-Fc inside, leading to a robust capsule structure that is less collapsed in the dry state. This single-component microcapsule is stabilized by the hydrophobic aggregation of Fc moieties and the protection of hydrophilic PAH backbones. Because of the excellent redox properties of Fc, the PAH-Fc microcapsules showed redox sensitivity to oxidation and reduction, as confirmed by UV-vis absorption spectroscopy and confocal laser scanning microscopy, resulting in reversible swelling and shrinking (11.7 vs 5.5 μm) in their size. Consequently, the permeability was also reversibly tuned, leading to the controlled loading and release of desired substances such as dextran.

Robust, Double-Walled Microcapsules for Self-Healing Polymeric Materials

Double-walled polyurethane/poly(urea-formaldehyde) microcapsules (PU/UF) are prepared for use in self-healing materials. This modified encapsulation procedure combines two chemistries to form more robust capsule shell walls in a single operation. Robust capsules are formed by this procedure as long as the aromatic polyisocyanate prepolymer is soluble in the core liquid and the core liquid is compatible with isocyanates. Compared to a standard UF encapsulation, the modified procedure results in capsules with an increase in shell wall thickness from 200 to 675 nm as a function of the amount of PU added to the core liquid. Thermal stability of PU/UF microcapsules prepared with varying amounts of PU is compared to UF microcapsules. Mechanical properties of the PU/UF microcapsules are assessed from single-capsule compression testing.

Robust Capsule and Fill Tube Assemblies for the National Ignition Campaign

The National Ignition Facility (NIF) tuning and ignition capsules will be gas filled through a laser precision drilled hole with a fill tube attached. To field these targets, several physics and assembly requirements must be met. These requirements drive the morphology of the final capsule and fill tube assembly (CFTA). Unexpectedly, they have also driven the need for a fill tube-transition tube subassembly, which is significant in the extra time required for fabrication. We have implemented engineering solutions that allow successful fabrication, testing, and transportation of CFTAs. During fabrication the fill tube is vertically inserted into both the transition tube and capsule, it is adhered with a low-viscosity adhesive, and there is a gap between mating surfaces. Nitrogen backpressure is flowed through the transition tube to prevent wicking of adhesive into the fill tube and to prevent partial restriction of flow or plugging. A nitrogen purge has also been implemented to displace atmospheric oxygen, which would otherwise absorb into the adhesive surface, truncate the polymerization process, and lead to a partially cured joint. Prior to transportation, the CFTA must complete a series of testing that simulates final assembly and NIF conditions: (a) helium leak test at room temperature, (b) helium leak test at liquid nitrogen temperature, (c) pressure test, and (d) X-ray fluorescence testing. The CFTA is transported in a custom device that provides vital support for the fill tube-to-capsule interface.

Immune protection of the brain--efficient and delicate.

The brain is in general considered the body's noblest organ. Its parenchyma is densely packed with electrically active neurons and glial cells that constantly undergo spatial rearrangements, but there is little connective tissue. The brain is vulnerable; it requires a particular degree of protection. Quite obviously, the brain is protected against external physical forces by a robust capsule formed by skull bones and meninges. Less obvious and by no means trivial is how the body protects its brain from endogenous danger, for example microbial infection. In fact, there has been a longstanding debate concerning the existence of immune reactivity within the central nervous system (CNS). In 1986, my colleagues and I reviewed the traditional concept of neuroimmunology?that the CNS was an immunoprivileged site, excluded from immune surveillance, and inaccessible to immunocompetent migratory cells [1]. The evidence supporting the concept of immunologic privilege rested on three structural peculiarities that distinguish the CNS from other tissues. First, there is a specialized endothelial bloodbrain barrier (BBB) that secludes the CNS parenchyma from the circulating blood and prevents most blood components from entering the tissue. Second, the CNS lacks fully organized drainage via lymphatic vessels. These are of crucial importance for the transport of antigen-presenting (dendritic) cells to travel from peripheral tissues to immune organs, where they trigger a full immune response. Third, major histocompatibility complex (MHC) determinants are conspicuously absent in the mature CNS. Without MHC proteins expressed on cell membranes, there is no presentation of antigenic peptide to specific T lymphocytes. Perhaps of even more importance, professional antigen-presenting cells, the cells specialized for the transport of peripheral antigen to immune organs and for activation of antigen-inexperienced naive T cells, are missing in the CNS. A wealth of recent information indicates that the BBB, lack of lymphatic drainage, and the lack of MHC antigens by no means reflect an absolute absence of immune reactivity within

Numerical study of fast ignition of ablatively imploded deuterium–tritium fusion capsules by ultra-intense proton beams

Compression and ignition of deuterium–tritium fuel under conditions relevant to the scheme of fast ignition by laser generated proton beams [Roth et al., Phys. Rev. Lett. 86, 436 (2001)] are studied by numerical simulation. Compression of a fuel containing spherical capsule driven by a pulse of thermal radiation is studied by a one-dimensional radiation hydrodynamics code. Irradiation of the compressed fuel by an intense proton beam, generated by a target at distance d from the capsule center, and subsequent ignition and burn are simulated by a two-dimensional code. A robust capsule, absorbing 635 kJ of 210 eV (peak) thermal x rays, with fusion yield of almost 500 MJ, has been designed, which could allow for target gain of 200. On the other hand, for a reasonable proton spectrum the required proton beam energy Eig, exceeds 25 kJ (for d=4 mm), even neglecting beam losses in the hohlraum and assuming that the beam can be focused on a spot with radius of 10 μm. The effects of proton range lengthening due to the increasing plasma temperature and of beam temporal spread caused by velocity dispersion are discussed. Ways to reduce Eig to about 10 kJ are discussed and analyzed by simulations.